The aims of this research project are: (1) to determine the origin of fetal unsaturated fatty acids, (2) to describe the development of the fatty acid desaturase and elongation systems in the fetus and neonate, (3) to describe the effects of pregnancy on maternal fatty acid desaturase and elongation, and (4) to determine the effects of maternal diabetes on the above three. This research will utilize both in vivo and in vitro studies on the synthesis and transport of unsaturated fatty acids, particularly essential fatty acids, in pregnant animals (rats, guinea pigs, and rabbits). Fatty acid elongation and desaturase systems will be assayed in the homogenates and subcellular fractions of maternal and fetal organs (liver, adipose tissue and placenta) at various gestational ages and in the neonate. The concentrations of the several protein components of the fatty acid desaturase systems of the various organs will be compared with the desaturase activity at different gestational ages. In vivo experiments will include acute preparations in which radioactive unsaturated fatty acids will be injected into the blood of the mother or fetus, followed by isolation and scintillation counting of the various lipid fractions of the plasma and organs. These experiments should allow estimation of the relative rates of placental transport of each fatty acid tested as well as the rates of maternal and fetal interconversions of essential fatty acids. Injection of tritiated water into the pregnant animals, followed by analysis of the tritium incorporation into unsaturated fatty acids of the maternal and fetal organs and plasma may allow determination of the relative contributions of maternal and fetal synthesis. Diabetes may be induced in the smaller animals by administration of alloxan or streptozotocin to the pregnant mothers prior to the development of Beta cells in fetal pancreas. The effect of this maternal alloxan diabetes on the above experiments, as well as the level of unsaturated fatty acids in maternal and fetal plasma will then be determined. The effect of human diabetes on the serum levels of essential fatty acids (polyunsaturates) in pregnant women, as well as in the cord blood of their infants will be determined.